Characterization of a pinhole tomograph with 180° acquisition using a discrete vertex set reconstruction algorithm
Bibliographic record
Abstract
Pinhole single photon emission computed tomography (SPECT) offers attractions for thyroid imaging, but acquisition must be limited to 180/spl deg/. The authors have mounted a 3.2 mm pinhole collimator on a rotating gamma camera, magnification 2.1, and characterized its response in the 10 cm field of view (FOV) by imaging points, lines, and a Picker thyroid phantom, comparing both full and half circle data acquisition. Image reconstruction was done with a new Discrete Vertex Set (DVS) algorithm and the Feldkamp (FDK) algorithm. For full circle acquisition, spatial resolution is quite uniform across the FOV, averaging 5.3 mm FWHM, and the reconstructed images show an intensity variation less than 5% in all directions. For this level of noise, the FDK and DVS algorithms perform similarly. For half circle reconstruction, spatial resolution shows more variation across the FOV, averaging 5.4 mm FWHM, and the maximum intensity variation is 20%. Differences between the FDK and DVS algorithms are more apparent. The thyroid phantom and its cold spots can be visualized in both full and half circle reconstructions, allowing size determination.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".